Your best bet is to take the cameras out of their boxes and out of the foil wrappers and put them into plastic ziploc bags if you want. Then ask the screeners to hand-inspect them. They will tell you that it is ok to put them through the machine but insist that they be hand-inspected. There was a thread around with many reports of film getting damaged even though the screeners said it would be ok. Better safe than sorry, I always say. The screeners are REQUIRED to hand-inspect film and cameras, and if they refuse, politely ask for a supervisor.
At any rate, do NOT put them into checked luggage as this could be x-rayed as well and the x-rays for the checked luggage are much more powerful and will surely ruin any film.
One other tip I often suggest is getting some mailers from mail-order film developers like Snapfish and sending the cameras to them once they have been used. That way you don't have to worry about them on the return trip, and your pictures could even be waiting for you when you get home!
